Diaminobenzene derivative, polyimide obtained therefrom, and liquid-crystal alignment film

ABSTRACT

An alkyldiamine having excellent polymerization reactivity, a polyimide comprising it as a constituting element, and a liquid crystal alignment film excellent in uniformity of liquid crystal alignment, are presented. Namely, the present invention relates to a diaminobenzene derivative represented by the following general formula (1) and to a polyimide obtained by reacting a diamine containing at least 1 mol % of the diaminobenzene derivative represented by the general formula (1), with at least one compound selected from a tetracarboxylic. dianhydride and its derivatives, to obtain a polyimide. precursor having a reduced viscosity of from 0.05 to 5.0 dl/g (in N-methylpyrrolidone at a temperature of 30° C., concentration: 0.5 g/dl) and ring-closing it, and having a repeating unit represented by the general formula (2). Further, the present invention relates to a liquid crystal alignment film containing at least 1 mol % of the above repeating unit.

TECHNICAL FIELD

The present invention relates to a novel diaminobenzene derivative, apolyimide synthesized by using the compound as one of stating materials,and a liquid crystal alignment film containing the polyimide. Moreparticularly, it relates to a diamine having a specific structure, whichis industrially readily producible, a polyimide employing it, and aliquid crystal alignment film. The polyimide synthesized by using thediamine of the present invention, is particularly useful for analignment film of a liquid crystal display device.

BACKGROUND ART

Heretofore, polyimides have been widely used as protecting materials orinsulating materials in the electric and electronic fields, by virtue ofhigh mechanical strength, heat resistance and solvent resistance, astheir characteristics. However, developments in the electric andelectronic fields in recent years have been remarkable, and increasinglyhigh properties have been required also for materials to be used.Especially in the application to alignment films for liquid crystaldisplay devices, polyimides have been mainly employed because of theuniformity and durability of the coating film surface. However, in anattempt for high densification and high performance of liquid crystaldisplays, the surface properties of polyimide coating films have becomeimportant, and it has become necessary to impart a new property whichconventional polyimides do not have.

A liquid crystal display device is a display device utilizing anelectro-optical change of liquid crystal and has undergone a remarkabledevelopment as a display device for various displays in recent years inview of the characteristics such that it is small in size and light inweight as a device and its power consumption is small. Especially, atwisted nematic type (TN-type) electric field effect liquid crystaldisplay device is a typical example, wherein nematic liquid crystalhaving positive dielectric anisotropy is employed so that liquid crystalmolecules are aligned in parallel with a substrate at the interface ofeach of a pair of mutually opposing electrode substrates, and the twosubstrates are combined so that the directions for alignment of liquidcrystal molecules are orthogonal to each other.

In such a TN-type liquid crystal display device, it is important thatlong axis directions of liquid crystal molecules are aligned uniformlyin parallel with the substrate surface and further that the liquidcrystal molecules are aligned with a certain inclined alignment angle(hereinafter referred to as a tilt angle) against the substrate. Astypical methods for aligning liquid crystal molecules in such a manner,two methods have been known heretofore.

The first method is a method which comprises vapor depositing aninorganic substance such as silicon oxide from an oblique direction to asubstrate to form an inorganic film on the substrate, so that the liquidcrystal molecules are aligned in the direction of vapor deposition. Thismethod is not industrially efficient, although uniform alignment with aconstant tilt angle can be obtained.

The second method is a method which comprises forming an organic coatingfilm on a substrate surface, and rubbing its surface in a predetermineddirection with a cloth of e.g. cotton, nylon or polyester, so thatliquid crystal molecules are aligned in the rubbing direction. By thismethod, constant alignment can be obtained relatively easily, andindustrially, this method is primarily employed. As the organic film,polyvinyl alcohol, polyoxyethylene, polyamide or polyimide may, forexample, be mentioned. However, from the viewpoint of the chemicalstability, thermal stability, etc., polyimide is most commonly employed.

In the field of liquid crystal alignment films, it has been difficult toobtain a high tilt angle constantly by the method of rubbing an organicfilm such as polyimide. As a means to solve such difficulty,JP-A-62-297819 proposes a treating agent for liquid crystal alignmentmade of a mixture of a long chain alkyl compound with a polyimideprecursor. Further, JP-A-64-25126 discloses a treating agent for liquidcrystal alignment made of a polyimide using, as a starting material, adiamine having an alkyl group. Thus, many attempts have been made toincrease the tilt angle of liquid crystal by introducing an alkyl groupinto polyimide, and it has been made possible to increase the tiltangle.

In recent years, there have been remarkable developments in the TNdisplay device, and many new properties are now required also for aliquid crystal alignment film. Among them, it has been increasinglyimportant to satisfy stabilization of the tilt angle and improvement inthe uniformity of alignment simultaneously, from the viewpoint ofimprovement of the essential properties of the liquid crystal alignmentfilm. As is evident also from JP-A-64-25126, an alkyl diamine which hasbeen heretofore been known and mainly used, is characterized in that analkyl group is connected to a phenylene diamine structure. However, if aconventional alkyl group-containing diamine is employed, there has beena problem that when a polyimide is to be synthesized, the alkyl groupacts as a steric hindrance, whereby the reactivity tends to be low, andit takes time for polymerization, or in some cases, polymerization doesnot proceed substantially. Taking time for the polymerization isproblematic from the viewpoint of the industrial production, and the lowpolymerization reactivity is problematic from the viewpoint of thedurability as an alignment film of polyimide. Further, whencopolymerization with another diamine is carried out, such a lowreactivity brings about a difference in the reaction rate. The resultingpolyimide is not necessarily uniform form the viewpoint of theuniformity of the repeating units. Consequently, when it is made into aliquid crystal alignment film, even if a desired tilt angle may beobtained, the film has not necessarily been satisfactory from theviewpoint of the uniformity of liquid crystal alignment.

These problems are extremely important subjects to be solved to furtherimprove the properties of a high quality, high precision liquid crystaldisplay device represented by a future TN device. Namely, it has beendesired to develop an alkyl diamine having an excellent reactivity, apolyimide containing it as a constituting element and a polyimide liquidcrystal orientation film, which contribute to the solution of suchproblems.

DISCLOSURE OF THE INVENTION

The present invention has been made under the above circumstances. Thepresent inventors have conducted extensive studies in detail andsystematically to accomplish the above object, and as a result, havecompleted the present invention.

Namely, the present invention relates to a diaminobenzene derivativerepresented by the general formula (1):

(wherein each of X and P which are independent of each other, is asingle bond or a bivalent organic group selected from —O—, —COO—, —OCO—,—CONH— and —NHCO—, Q is a C₁₋₂₂ straight chain alkyl group or straightchain fluoroalkyl group, a is an integer of from 1 to 4 and representsthe number of substituents, R is a substituent selected from fluorine, amethyl group and a trifluoromethyl group, and b is an integer of from 0to 4 and represents the number of substituents).

Further, the present invention relates to a polyimide obtained byreacting a diamine containing at least 1 mol % of a diaminobenzenederivative represented by the general formula (1):

(wherein each of X and P which are independent of each other, is asingle bond or a bivalent organic group selected from —O—, —COO—, —OCO—,—CONH— and —NHCO—, Q is a C₁₋₂₂ straight chain alkyl group or straightchain fluoroalkyl group, a is an integer of from 1 to 4 and representsthe number of substituents, R is a substituent selected from fluorine, amethyl group and a trifluoromethyl group, and b is an integer of from 0to 4 and represents the number of substituents), with at least onecompound selected from a tetracarboxylic dianhydride and itsderivatives, to obtain a polyimide precursor having a reduced viscosityof from 0.05 to 5.0 dl/g (in N-methylpyrrolidone at a temperature of 30°C., concentration: 0.5 g/dl) and ring-closing it, and having a repeatingunit represented by the general formula (2):

(wherein A is a tetravalent organic group constituting a tetracarboxylicacid, and B is a bivalent organic group constituting a diamine).

Still further, the present invention relates to a liquid crystalalignment film containing the above polyimide.

Now, the present invention will be described in detail.

The diaminobenzene derivative of the present invention can be easilysynthesized and is useful as a starting material for e.g. a polyimide ora polyamide. Further, this may be used as one of starting materials to aobtain a polyimide having an alkyl group or a fluoroalkyl group as aside chain. This polyimide is useful for e.g. an insulating film for asemiconductor or a heat resistant protective film for an optical device,but is particularly useful as an alignment film for a liquid crystaldisplay device, and it has excellent characteristics such that not onlypolymerization is quick at the time of the preparation of a polyimideprecursor, but also a high tilt angle can easily be provided, andalignment of liquid crystal is good.

Particularly, the present invention has an important object to obtain apolyimide having a desired repeating unit quickly by using a specificdiaminobenzene derivative having an alkyl group and to realizeuniformity of alignment and a high tilt angle imparted to liquidcrystal, by using the specific polyimide obtainable from the diamine, asa liquid crystal alignment film. For this purpose, Q in the generalformula (1) is a C₁₋₂₂ straight chain alkyl group. This is essential tocontrol the degree of the tilt-angle, and such a group is connected tothe polyimide main chain via a connecting portion P. Further, X isessential to connect a p-aminophenyl group. Further, R is necessary tocontrol the surface property of the polyimide within a range not toimpair the nucleophilic nature of an amino group, when a polymerizationreactivity with a tetracarboxylic dianhydride and its derivative istaken into consideration.

The diaminobenzene derivative represented by the general formula (1):

(wherein each of X and P which are independent of each other, is asingle bond or a bivalent organic group selected from —O—, —COO—, —OCO—,—CONH— and —NHCO—, Q is a C₁₋₂₂ straight chain alkyl group or straightchain fluoroalkyl group, a is an integer of from 1 to 4 and representsthe number of substituents, R is a substituent selected from fluorine, amethyl group and a trifluoromethyl group, and b is an integer of from 0to 4 and represents the number of substituents), is a diamine having aspecific structure, and it comprises the following two amine portions:

(wherein R and b are the same as in the formula (1)), a connectingportion X and the following alkyl or fluoroalkylbenzene portion:

(wherein P, Q and a are the same as in the formula (1)). Its syntheticmethod is not particularly limited. For example, it can be synthesizedby the following method.

Namely, in a synthesis of a diamine, it is common to synthesize thecorresponding dinitro compound represented by the general formula (3):

(wherein X, P, Q, a and b are the same as in the formula (1)), and toreduce the nitro groups by a usual method to convert them into aminogroups.

Here, each of a and b which are independent of each other, representsthe number of substituents; a is selected from integers of from 1 to 4but is preferably 1 or 2 from the viewpoint of the surface property; andb is likewise selected from integers of from 0 to 2.

Each of connecting portions X and P which are independent of each other,is a connecting group such as a single bond, an ether bond —O—, an esterbond —COO—, a reverse ester bond —OCO—, an amide bond —CONH— or areverse amide bond —NHCO—. From the viewpoint of the polymerizationreactivity, an ether bond, an ester bond or an amide bond isparticularly preferred.

Such a connecting group can be formed by a usual organic syntheticmethod. For example, in the case of an ether bond, it is common to reactthe corresponding halogen derivative and hydroxyl group-substitutedderivative in the presence of an alkali, and in the case of an amidebond, it is common to react the corresponding acid chloride and aminogroup-substituted derivative in the presence of an alkali. Further, forthe single bond, various methods are available, and common organicsynthetic methods such as a Grignard reaction, a Friedel-Craftsacylation method of an aromatic ring, a Kishner reduction method and across coupling method, may be employed to suitably carry out theconnection.

A specific example of the material for forming the dinitro moiety, is abenzene containing substituent Q and connecting group P, di-substitutedby substituents for forming the connecting portions X such as halogenatoms, hydroxyl groups, amino groups, carboxyl groups, halogenated acylgroups or carbonyl groups, and such a benzene is connected to asubstituted p-nitro benzene derivative to obtain a desired dinitrocompound.

Specific examples of the di-substituted benzene derivative include3,5-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid chloride,3,5-dicarboxyphenol, 3,5-diaminobenzoic acid and 3,5-diaminophenol.Further, the p-nitrobenzene derivative may, for example, bep-nitrofluorobenzene, p-nitrochlorobenzene, p-nitrobromobenzene,p-nitroiodobenzene, p-nitrophenol, p-nitrobenzoic acid, p-nitrobenzoicacid chloride, 2-methyl-4-nitrophenol, 2-trifluoromethyl-4-nitrophenol,2-methyl-4-nitrobenzoic acid, 2-methyl-4-nitrobenzoic acid chloride,2-trifluoromethyl-4-nitrobenzoic acid, 2-trifluoromethyl-4-nitrobenzoicacid chloride or acetanilide. A combination thereof may be suitablyselected depending upon the particular purpose taking into considerationthe reactivity and the availability of the materials. It should bementioned that those exemplified here are only examples.

The chain substituent Q in the general formula (1) is a C₁₋₂₂ straightchain alkyl group or straight chain fluoroalkyl group. The carbon numbercan be suitably selected in order to obtain the desired tilt angle whenthe corresponding polyimide is used as an alignment film.

The diaminobenzene derivative of the present invention represented bythe above general formula (1) obtainable by the method as describedabove, may be subjected to polycondensation with a tetracarboxylic aciddianhydride and its derivative, such as tetracarboxylic dianhydride, atetracarboxylic dihalide or tetracarboxylic acid, to synthesize apolyimide having a specific structure at its side chain.

The method for obtaining the polyimide of the present invention, is notparticularly limited. Specifically, it can be obtained by reacting andpolymerizing the above diamine with at least one compound selected froma tetracarboxylic dianhydride and its derivatives, to obtain a polyimideprecursor, followed by ring-closing imide conversion.

The tetracarboxylic dianhydride and its derivatives to be used to obtainthe polyimide of the present invention, are not particularly limited.

Specific examples thereof include aromatic tetracarboxylic dianhydridessuch as pyromellitic dianhydride, 2,3,6,7-naphthalene tetracarboxylicdianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride,2,3,6,7-anthracene tetracarboxylic dianhydride, 1,2,5,6-anthracenetetracarboxylic dianhydride, 3,3′,4,4′-biphenyl tetracarboxylicdianhydride, 2,3,3′,4-biphenyl tetracarboxylic dianhydride,bis(3,4-dicarboxyphenyl)ether dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)sulfonedianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride,2,2-bis(3,4-dicarboxyphenyl)propane dianhydride,1,1,1,3,3,3-hexafloro-2,2-bis(3,4-dicarboxyphenyl)propane dianhydride,bis(3,4-dicarboxyphenyl)dimethyl silane dianhydride,bis(3,4-dicarboxyphenyl)diphenyl silane dianhydride, 2,3,4,5-pyridinetetracarboxylic dianhydride, and 2,6-bis(3,4-dicarboxyphenyl)pyridinedianhydride, and their tetracarboxylic acids and their dicarboxylic aciddiacid halides; alicyclic tetracarboxylic dianhydrides such as1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylicdianhydride, 2,3,5-tricarboxycyclopentyl acetic dianhydride, and3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride, andtheir tetracarboxylic acids and their dicarboxylic acid diacid halides;and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-buthanetetracarboxylic dianhydride, and their tetracarboxylic acids and theirdicarboxylic acid diacid halides.

Especially for application to alignment films, alicyclic tetracarboxylicdianhydrides, and their tetracarboxylic acids and their dicarboxylicacid diacid halides are preferred from the viewpoint of the transparencyof the coating film. Particularly preferred are 1,2,3,4-cyclobutanetetracarboxylic dianhydride,3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride,bicyclo[3,3,0]-octane-tetracarboxylic dianhydride and3,5,6-tricarboxynorbornane-2:3,5:6 dianhydride. Further, one or more ofthese tetracarboxylic dianhydrides and their derivatives may be used inadmixture.

In the present invention, the tetracarboxylic dianhydride and itsderivative may be copolymerized with the diaminobenzene derivativerepresented by the general formula (1) (hereinafter referred to simplyas the diamine(1)) and other common diamines (hereinafter referred tosimply as common diamines).

The common diamines to be used here are primary diamines commonly usedfor the synthesis of polyimides, and they are not particularly limited.Specific examples thereof include aromatic diamines such asp-phenylenediamine, m-phenylenediamine, 2,5-diaminotoluene,2,6-diaminotoluene, 4,4′-diaminobiphenyl,3,3′-dimethyl-4,4′-diaminobiphenyl, 3,3′-dimetoxy-4,4′-diaminobiphenyl,diaminodiphenylmethane, diaminodiphenyl ether,2,2′-diaminodiphenylpropane, bis(3,5-diethyl-4-aminophenyl)methane,diaminodiphenylsulfone, diaminobenzophenone, diaminonaphthalene,1,4-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenyl)benzene,9,10-bis(4-aminophenyl)anthracene, 1,3-bis(4-aminophenoxy)benzene,4,4′-bis(4-aminophenoxy)diphenylsulfone,2,2-bis[4-(4-aminophenoxy)phenyl]propane,2,2-bis(4-aminophenyl)hexafluropropane and2,2-bis[4-(4-aiminophenoxy)phenyl]hexafluropropane; aliphatic diaminessuch as bis(4-aminocyclohexyl)methane andbis(4-amino-3-methylcyclohexyl)methane, and aliphatic diamines such astetramethylenediamine and hexamethylenediamine; as well asdiaminocycloxanes such as

(wherein m is an integer of from 1 to 10). Further, these diamines maybe used alone or in combination as a mixture of two or more of them.

By adjusting the proportion of the molar amount of the diamine (1) inthe total molar amount of diamines used at the time of polymerization ofthe polyimide of the present invention, the surface property of thepolyimide such as water repellency can be modified, and further in acase where it is used as a liquid crystal alignment film, wettabilitywith liquid crystal, and further, the tilt angle of liquid crystal, canbe increased. The proportion of the molar amount of the diamine (1) inthe total molar amount of diamines to be used here, is at least 1 mol %.

Further, when it is used as a liquid crystal alignment film, it iscommon to adjust the proportion of the molar amount of the diamine (1)in the total molar amount of diamines to be used, to be within a rangeof from 1 mol % to 100 mol % from such a viewpoint that a polyimidehaving a practically suitable degree of polymerization can easily beobtained, or that the tilt angle required in a common liquid crystaldisplay system (such as a twisted nematic system) is usually at a levelof from a few degrees to about 10 degrees in many cases, although it maydepend also on the number of alkyl of Q. Further, in the case of aperpendicular alignment system, the molar amount of the diamine (1) isusually from 40 mol % to 100 mol %.

The tetracarboxylic dianhydride and its derivative, and the abovementioned diamine, are reacted and polymerized to obtain a polyimideprecursor, and then this is converted to an imide by ring closure. Asthe tetracarboxylic dianhydride and its derivative to be used here, itis common to employ tetracarboxylic dianhydride. The ratio of the molaramount of the tetracarboxylic dianhydride to the total molar amount ofthe diamine (1) and common diamines, is preferably from 0.8 to 1.2. Likein a usual polycondensation reaction, the polymerization degree of theresulting polymer tends to be large, as the molar ratio becomes close to1.

If the polymerization degree is too small, the strength of the polyimidefilm tends to be inadequate. On the other hand, if the polymerizationdegree is too large, the operation efficiency at the time of formationof the polyimide film tends to be poor in some cases. Accordingly, thepolymerization degree of the product in this reaction is preferably from0.05 to 5.0 dl/g (in N-methylpyrrolidone at a temperature of 30° C.,concentration: 0.5 g/dl) as calculated as the reduced viscosity of thepolyimide precursor solution.

A method for reacting and polymerizing the carboxylic dianhydride andthe above diamine, is not particularly limited. It is common to employ amethod wherein the above diamine is dissolved in an organic polarsolvent such as N-methylpyrrolidone, N,N-dimethylacetamide orN,N-dimethylformamide, and to the solution, the tetracarboxylicdianhydride is added and reacted to synthesize a polyimide precursor,followed by dehydration ring closure for conversion to an imide.

The reaction temperature at the time of the reacting the tetracarboxylicdianhydride and the above mentioned diamine to obtain a polyimideprecursor, may be an optional temperature selected within a range offrom −20 to 150° C., preferably from −5 to 100° C. Further, thispolyimide precursor is subjected to dehydration under heating at atemperature of from 100 to 400° C., or subjected to chemicalimide-conversion by means of an imide-conversion catalyst such aspyridine/acetic anhydride, which is commonly used, to obtain apolyimide. In such a case, the imide conversion can be controlledoptionally within a range of from 0 to 100% by reaction conditions. Inan application to an alignment film, the imide conversion is preferablyfrom 60 to 100%.

When the polyimide of the present invention is to be used as aninsulating film or a protecting film for an electric or electronicelement, or as an alignment film for a liquid crystal display device, itis necessary to form a polyimide coating film having a uniform filmthickness on a substrate.

To form this polyimide coating film, it is usually possible to form apolyimide coating film by coating the polyimide precursor solution byitself on a substrate and heating it for imide-conversion on thesubstrate. The polyimide precursor solution to be used here may be theabove polymer solution by itself, or the formed polyimide precursor maybe put into a large excess amount of a poor solvent such as water ormethanol to precipitate and recover it, and then it may be used asre-dissolved in a solvent. The solvent for diluting the above polyimideprecursor solution and/or the solvent for re-dissolving the precipitatedand recovered polyimide precursor, is not particularly limited so longas it is capable of dissolving the polyimide precursor.

Specific examples of such solvents include N-methylpyrrolidone,N,N-dimethylacetoamide, and N,N-dimethylformamide. These solvents may beused alone or as mixed. Further, even in the case of a solvent which isincapable of presenting a uniform solution by itself, such a solvent maybe added and used within a range where a uniform solution can beobtained. As such an example, ethyl cellosolve, butyl cellosolve, ethylcarbitol, butyl carbitol, ethyl carbitol acetate or ethylene glycol maybe mentioned. Further, for the purpose of improving the adhesion of thepolyimide film to the substrate, it is of course preferred to add anadditive such as a coupling agent to the obtained polyimide precursorsolution. Further, an optional temperature within a range of from 100 to400° C. may be employed as the temperature for heating forimide-conversion on the substrate. However, particularly preferred iswithin a range of from 150 to 350° C.

On the other hand, in a case where the polyimide of the presentinvention is soluble in a solvent, the polyimide precursor obtained bythe reaction of the tetracarboxylic dianhydride and the above mentioneddiamine, may be imide-converted in the solvent to obtain a polyimidesolution. To convert the polyimide precursor to a polyimide in thesolution, it is common to employ a method wherein dehydrationring-closure is carried out by heating. This ring closure temperature bydehydration under heating may be an optional temperature selected withina range of from 150 to 350° C., preferably from 120 to 250° C. Asanother method for converting the polyimide precursor to the polyimide,it is possible to carry out ring closure chemically by means of a knowndehydration ring-closing catalyst.

The polyimide solution thus obtained, may be used by itself, or may beprecipitated and isolated in a poor solvent such as methanol or ethanol,and then it may be used as re-dissolved in a proper solvent. The solventfor re-dissolution is not particularly limited so long as it is capableof dissolving the polyimide, but as an example, 2-pyrorridone, N-methylpyrrolidone, N-ethyl pyrrolidone, N-vinyl pyrrolidone, N,N-dimethylacetoamide, N,N-dimethylformamide or γ-butyrolactone may be mentioned.

Further, even a solvent which is incapable of dissolving this polyimideby itself, may be added to the above solvent within a range not toimpair the solubility. As such an example, ethyl cellosolve, butylcellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate orethylene glycol may be mentioned.

Further, for the purpose of further improving the adhesion of thepolyimide film to the substrate, it is of course preferred to add anadditive such as a coupling agent to the obtained polyimide solution.

This solution is coated on a substrate, and the solvent is evaporated,whereby a polyimide coating film can be formed on the substrate. Thetemperature at that time may be sufficient so long as the solvent can beevaporated, and usually a temperature of from 80 to 150° C. issufficient.

Further, when it is used as a liquid crystal alignment film, a polyimidefilm having a film thickness of from 100 to 3000 Å, is formed on atransparent substrate of e.g. glass or plastic film provided withtransparent electrodes, and then, the polyimide film is, subjected torubbing treatment to obtain a liquid crystal alignment film.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in further detail withreference to Examples, but the present invention is by no meansrestricted to such Examples.

Syntheses of Diamines EXAMPLE 1

(Synthesis of n-dodecyl[3,5-bis(4-aminobenzoylamino)]benzoate) (4)

Into a 500 ml flask, 1-dodecanol (65.01 g, 348.9 mmol), triethylamine(44.00 g, 435.0 mmol) and tetrahydrofuran (410 ml) were added to obtaina uniform solution, and then, a THF solution (80 ml) of 3,5-benzoylchloride (80.16 g, 347.7 mmol) was dropwise added. Thereafter, refluxingand stirring were continued for 2.5 hours. The reaction solution waspoured into water, and the precipitated solid was separated byfiltration and re-crystallized from acetonitrile to obtain colorlesscrystals (121.12 g, yield: 82%). From the IR and NMR spectra, thecrystals were confirmed to be n-dodecyl-3,5-dinitrobenzoate (1). Meltingpoint: 64° C.

Dioxane (250 ml) was added to n-dodecyl-3,5-dinitrobenzoate (1) (25.13g, 59.2 mmol), and to this solution, Pd—C (1.51 g) was added in anitrogen atmosphere, followed by stirring for 7 hours in a hydrogenatmosphere. Pd—C was filtered off, and the filtrate was poured intowater, and the precipitated crystals were corrected by filtration. Afterdrying, they were re-crystallized from n-hexane to obtain slightlyyellow crystals (18.46 g, yield: 79%). From the IR and NMR spectra, thecrystals were confirmed to be n-dodecyl-3,5-diaminobenzoate (2). Meltingpoint 64° C.

Into a 200 ml flask, n-dodecyl-3,5-diaminobenzoate (2) (8.01 g, 20.3mmol), triethylamine (4.57 g, 45.2 mmol), and tetrahydrofuran (100 ml)were added to obtain a uniform solution, and then, a THF solution (50ml) of 4-nitrobenzoyl chloride (7.93 g, 42.8 mmol) was dropwise added.Thereafter, refluxing and stirring were continued for 6 hours. Thereaction solution was poured into water, and the precipitated solid wascollected by filtration and recrystallized from acetonitrile to obtainslightly yellow crystals (10.15 g, yield: 81%). From the IR and NMRspectra, the crystals were found to ben-dodecyl[3,5-bis(4-nitrobenzoylamino)]benzoate (3).

Melting point: 189° C.

Dioxane (160 ml) was added ton-dodecyl[3,5-bis(4-nitrobenzoylamino)]benzoate (3) (7.99 g, 12.9 mmol),and to this solution, Pd—C (0.87 g) was added in a nitrogen atmosphere,followed by stirring for 4 hours in a hydrogen atmosphere. Pd—C wasfiltered off, and then, the filtrate was poured into water, and theprecipitated crystals were collected by filtration. After drying, theywere recrystallized from THF-n-hexane to obtain slight yellow crystals(4.25 g, yield: 65%). From the IR and NMR spectra, these crystals werefound to be the desired n-dodecyl[3,5-bis(4-aminobenzoylamino)]benzoate(4) (melding point: 186° C.).

The analytical results are shown below.

¹H-NMR (d-DMSO, δ ppm): 9.9 (2H, s), 8.6 (1H, s), 8.1 (2H, s), 7.8 (4H,d), 6.6 (4H, d), 5.8 (4H, s), 4.3 (2H, t), 1.7 (2H, m), 1.2-1.4 (18H,broad), 0.8 (3H, t).

IR (KBr, cm⁻¹): 3445, 3387, 3351 (NH₂), 3304, 3200 (NH), 2955, 2922,2853 (CH₂), 1710 (COO), 1640, 1608 (CONH).

EXAMPLE 2

(Synthesis of n-hexyl[3,5-bis(4-aminobenzoylamino)]benzoate)

Using 3,5-dinitrobenzoyl chloride (74.3 g, 322.5 mmol) and hexyl alcohol(33.0 g, 323.6 mmol), n-hexyl-3,5-dinitrobenzoate was obtained (81.1 g,yield: 85%) in the same manner as in Example 1.

Using the obtained dinitro compound (33.4 g, 112.8 mmol), reduction wascarried out in the same manner as in Example 1, followed byrecrystallization to obtain n-hexyl-3,5-diaminobenzoate (25.6 g, yield:96%).

Using n-hexyl-3,5-diaminobenzoate (24.0 g, 101.7 mmol) and4-nitrobenzoyl chloride (39.7 g, 214.4 mmol),n-hexyl[3,5-bis(4-nitrobenzoylamino)]benzoate was obtained (44.5 g,yield: 82%) in the same manner as in Example 1.

Finally, this dinitro compound (20.4 g, 38.2 mmol) was reduced in thesame manner as in Example 1, followed by recrystallization to obtainn-hexyl[3,5-bis(4-aminobenzoylamino)] (5) was obtained (14.8 g, yield:82%).

Melding point: 208° C. The analytical results are shown below.

Mass (m/e): 474 (M+).

¹H-NMR (d-DMSO, δ ppm): 9.9 (2H, s), 8.6 (1H, s), 8.1 (2H, s), 7.8 (4H,d), 6.6 (4H, d), 5.8 (4H, s), 4.3 (2H, t), 1.7 (2H, m), 1.2-1.4 (6H,broad), 0.9 (3H, t).

IR (KBr, cm⁻¹): 3445, 3339, 3351 (NH₂), 3304, 3204 (NH), 2955, 2931(CH₂), 1694 (COO), 1645, 1605 (CONH).

EXAMPLE 3

(Synthesis of n-hexadecyl[3,5-bis(4-aminobenzoylamino)]benzoate (6))

Using 3,5-dinitrobenzoyl chloride (60.6 g, 263.0 mmol) and hexadecylalcohol (63.9 g, 263.9 mmol), n-hexadecyl-3,5-dinitrobenzoate wasobtained (103.2 g, yield: 90%) in the same manner as in Example 1.

Using the obtained dinitro compound (40.68 g, 93.3 mmol), reduction wascarried out in the same manner as in Example 1, followed byrecrystallization to obtain n-hexadecyl-3,5-diaminobenzoate (35.0 g,yield: 100%).

Using the diamine compound (16.7 g, 44.4 mmol) and 4-nitrobenzoylchloride (17.3 g, 93.6 mmol),n-hexadecyl[3,5-bis(4-nitrobenzoylamino)]benzoate was obtained (25.4 g,yield: 85%) in the same manner as in Example 1.

Finally, this dinitro compound (13.4 g, 19.9 mmol) was reduced in thesame manner as in Example 1, followed by recrystallization to obtainn-hexadecyl[3,5-bis(4-aminobenzoylamino)] (6) was obtained (12.0 g,yield: 98%).

Melting point: 139° C. The analytical results are shown below.

Mass (m/e): 614 (M+).

¹H-NMR (d-DMSO, δ ppm): 10.0 (2H, s), 8.6 (1H, s), 8.1 (2H, s), 7.8 (4H,d), 6.6 (4H, d), 5.8 (4H, s), 4.3 (2H, t), 1.7 (2H, m), 1.2-1.4 (26H,broad), 0.8 (3H, t).

IR (KBr, cm⁻¹): 3388, 3346 (NH₂), 3304, 3204 (NH), 2952, 2917, 2834(CH₂), 1708 ((COO) 1645, 1609 (CONH).

EXAMPLE 4

(Synthesis of n-dodecyl[3,5-bis(4-aminophenoxy)]benzoate) (10))

Into a 500 ml flask, 3,5-dihydroxymethyl benzoate (40.0 g, 238.1 mmol)obtained by a usual method, 4-fluoronitrobenzene (67.1 g, 475.8 mmol),potassium carbonate (65.4 g) and dimethylacetamide (350 ml) were added,followed by stirring at 95° C. for 9 hours. The reaction solution wassubjected to filtration, and the filtrate was left to stand for one day.The precipitated solid was collected by filtration and recrystallizedfrom ethyl acetate to obtain colorless solid3,5-bis(4-nitrophenoxy)methyl benzoate (7) (78.5 g, yield: 80%).

Melting point: 183° C.

Into a 1 l flask, the above dinitro compound (70.0 g, 170.7 mmol),sulfuric acid (17.5 g) and acetic acid (600 ml) were put, followed byrefluxing and stirring for 8 hours. The reaction solution was left tostand for one day, and the precipitated solid was collected byfiltration. Recrystallization from acetic acid was carried out to obtain3,5-bis(4-nitrophenoxy) benzoate (8) as colorless crystals (59.3 g,yield: 87%). Melting point: 230° C.

Into a 500 ml flask, 3,5-bis(4-nitrophenoxy) benzoate (8) (45.0 g, 114.0mmol) and thionyl chloride (250 ml) were put, and refluxed and stirredfor 3 hours. After completion of the reaction, excess thionyl chloridewas removed by distillation, and THF (400 ml) was added to the residue.This THF solution was dropwise added at 80° C. to a THF solution (100ml) of n-dodecyl alcohol (23.5 g, 126.3 mmol) and triethylamine (12.7 g,125.7 mmol). After completion of the dropwise addition, refluxing andstirring were carried out for 15 hours. The solution was concentratedand poured into water (1500 ml) and extracted with ethyl-acetate. Theorganic layer was washed with water and 1N sodium hydroxide and driedover anhydrous sodium sulfate. Further, the solvent was distilled offunder reduced pressure, and the residue was recrystallized fromacetonitrile to obtain n-dodecyl[3,5-bis(4-nitrophenoxy)]benrzoate) (9)(47.6 g, yield: 74%).

Melting point: 64° C.

Dioxane (3,00 ml) was added ton-dodecyl[3,5-bis(4-nitrophenoxy)]benzoate (9) (15.7 g, 27.8 mmol), andto this solution, Pd—C (1.7 g) was added in a nitrogen atmosphere,followed by stirring for 6 hours in a hydrogen atmosphere. Pd—C wasfiltered off, and the filtrate was poured into water, and theprecipitated crystals were collected by filtration. After drying, theywere recrystallized from acetonitrile to obtain slight yellow crystals(9.00 g, yield: 65%). Melting point: 49° C. From the IR, NMR and Massspectra, the crystals were found to be the desiredn-dodecyl[3,5-bis(4-aminobenzoylamino)]benzoate (10). The analyticalresults are shown below.

Mass (m/e): 504 (M+).

¹H-NMR (d-DMSO, δ ppm): 7.2 (2H, s), 6.9 (4H, d), 6.7 (1H, s), 6.6 (4H,d), 4.2 (2H, t), 3.8 (4H, s), 1.6 (2H, m), 1.1-1.3 (18H, broad), 0.9(3H, t).

IR (KBr, cm⁻¹): 3459, 3374 (NH₂), 3304, 3200 (NH), 2959, 2917, 2847(CH₂), 1708 (COO), 1216 (ArO).

EXAMPLE 5

(Synthesis of n-hexadecyl[3,5-bis(4-aminobenzoylamino)]benzoate (11))

Using 3,5-bis(4-nitrophenoxy)benzoate (8) (25.6 g, 64.6 mmol) obtainedin Example 4 and n-hexadecyl alcohol (17.3 g, 71.5 mmol),n-hexadecyl[3,5-bis(4-nitrophenoxy)]benzoate was obtained (32.4 g,yield: 81%) in the same manner as in Example 4.

Finally, this dinitro compound (16.4 g, 26.5 mmol) was reduced in thesame manner as in Example 4, followed by recrystallization to obtainn-hexadecyl[3,5-bis(4-aminophenoxy)]benzoate (11) (13.5 g, yield: 91%).The melting point: 54° C. The analytical results are shown below.

Mass (m/e): 560 (M+).

¹H-NMR (d-DMSO, δ ppm): 7.2 (2H, s), 6.8 (4H, d), 6.6 (1H, s), 6.5 (4H,d), 4.2 (2H, t), 3.8 (4H, s), 1.6 (2H, m), 1.1-1.4 (26H, broad), 0.9(3H, t).

IR (KBr, cm⁻¹): 3460, 3376 (NH₂), 3302, 3200 (NH), 2960, 2917, 2847(CH₂), 1708 (COO), 1216 (ArO).

EXAMPLE 6

(Preparation of a Polyimide)

5 g (10.5 mmol) of n-dodecyl[3,5-bis(4-aminobenzoylamino)]benzoateobtained in Example 1 and 2.1 g (10.5 g) of1,2,3,4-cyclobutanetetracarboxylic dianhydride were dissolved in 40 g ofN-methylpyrrolidone, followed by stirring at 20° C. for 8 hours to carryout a polycondensation reaction to obtain a polyimide precursorsolution.

The reduced viscosity of the obtained polyimide precursor was 0.80 dl/g(at a concentration of 0.5 g/dl in N-methylpyrrolidone at 30° C.).

This solution was heat-treated at 180° C. for one hour to obtain auniform polyimide coating film. The obtained coating film was subjectedto IR measurement and was confirmed to be a polyimide having a dodecylgroup.

EXAMPLE 7

5 g (10.5 mmol) of n-dodecyl[3,5-bis(4-aminobenzoylamino)]benzoateobtained in Example 1 and 2.6 g (10.5 mmol) ofbicyclo[3,3,0]-octane-tetracarboxylic dianhydride were dissolved in 40 gof N-methylpyrrolidone, followed by stirring at 20° C. for 8 hours tocarry out a polycondensation reaction to obtain a polyimide precursorsolution. The reduced viscosity of the obtained polyimide precursor was0.70 dl/g (at a concentration of 0.5 g/dl in N-methylpyrrolidone at 30°C.).

To this solution, acetic anhydride and pyrimidine were added as an imideconversion catalyst, followed by a reaction at 60° C. for one hour toobtain a soluble polyimide resin solution. This solution was put intomethanol, and the obtained precipitate was collected by filtrationand-dried to obtain a white polyimide powder.

This polyimide resin powder was confirmed to be 70% imide-converted, byNMR. Further, the obtained coating film was subjected to IR measurementand was confirmed to be a polyimide having a dodecyl group.

EXAMPLE 8

5 g (10.5 mmol) of n-dodecyl[3,5-bis(4-aminobenzoylamino)]benzoateobtained in Example 1 and 2.9 g (10.5 mmol) of3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride weredissolved in 40 g of N-methylpyrrolidone, followed by stirring at 20° C.for 8 hours to carry out a polycondensation reaction to obtain apolyimide precursor solution. The reduced viscosity of the obtainedpolyimide precursor was 0.75 dl/g (at a concentration of 0.5 g/dl inN-methylpyrrolidone at 30° C.)

To this solution, acetic anhydride and pyrimidine were added as animide-conversion catalyst, followed by a reaction at 60° C. for one hourto obtain a soluble polyimide resin solution. This solution was put into500 g of methanol, and the obtained precipitate was collected byfiltration and dried to obtain a white polyimide powder.

This polyimide resin powder was confirmed to be 90% imide-converted, byNMR. Further, the obtained coating film was subjected to IR measurementand confirmed to be a polyimide having a dodecyl group.

EXAMPLE 9

5 g (10.5 mmol) of n-dodecyl[3,5-bis(4-aminobenzoylamino)]benzoateobtained in Example 1 and 2.6 g (10.5 mmol) of3,5,6-tricarboxynorbornene-2:3,5:6 dianhydride were dissolved in 40 g ofN-methylpyrrolidone, followed by stirring at 20° C. for 8 hours to carryout a polycondensation reaction to obtain a polyimide precursorsolution. The reduced viscosity of the obtained polyimide precursor was0.55 dl/g (at a concentration of 0.5 g/dl in N-methylpyrrolidone at 30°C.).

To this solution, acetic anhydride and pyridine were added as an imideconversion catalyst, followed by a reaction at 60° C. for one hour toobtain a soluble polyimide resin solution. This solution was put into500 g of methanol, and the obtained precipitate was collected byfiltration and dried to obtain a white polyimide powder.

This polyimide resin powder was confirmed to be 90% imide-converted, byNMR. Further, the obtained coating film was subjected to IR measurementand confirmed to be a polyimide having a dodecyl group.

EXAMPLES 10 to 20

Using the diamines synthesized in Examples 2 to 5 and usingtetracarboxylic dianhydrides employed in Examples 6 to 9, polyimideswere synthesized in accordance with the respective Examples, andsubjected to IR measurements in accordance with Example 6 and confirmedto be the desired polyimides. In the following Table 1, the reducedviscosities of the precursor solutions of the polyimides (at aconcentration of 0.5 g/dl in N-methylpyrrolidone at 30° C.) will begiven.

TABLE 1 Tetracarboxylic Reduced viscosity Example No. Diaminedianhydride (dl/g) 10 Example 2 Example 6 1.05 11 Example 2 Example 70.82 12 Example 2 Example 8 0.77 13 Example 2 Example 9 0.60 14 Example3 Example 6 0.74 15 Example 3 Example 7 0.75 16 Example 3 Example 8 0.6517 Example 3 Example 9 0.53 18 Example 4 Example 6 1.14 19 Example 4Example 7 0.96 20 Example 4 Example 8 0.88 21 Example 4 Example 9 0.6722 Example 5 Example 6 1.03 23 Example 5 Example 7 0.89 24 Example 5Example 8 0.83 25 Example 5 Example 9 0.60

COMPARATIVE EXAMPLE 1

5 g (14.3 mmol) of hexadecyloxy-2,4-diaminobenzene as a diamine and 2.8g (14.3 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride weredissolved in 40 g of N-methylpyrrolidone, followed by stirring at 20° C.for 8 hours to carry out a polycondensation reaction to obtain apolyimide precursor solution. The reduced viscosity of the obtainedpolyimide precursor was as low as 0.35 dl/g (at a concentration of 0.5g/dl in N-methylpyrrolidone at 30° C.).

COMPARATIVE EXAMPLE 2

5 g (14.3 mmol) of hexadecyloxy-2,4-diaminobenzene as a diamine and 3.6g (14.3 mmol) of bicyclo[3,3,0]-octane-tetracarboxylic dianhydride weredissolved in 40 g of N-methylpyrrolidone, followed by stirring at 20° C.for 4 hours to carry out a polycondensation reaction, but polymerizationdid not substantially proceed, and only an oligomer was formed. Further,heating was carried out, but no improvement in effects was observed.

COMPARATIVE EXAMPLE 3

5 g (14.3 mmol) of hexadecyloxy-2,4-diaminobenzene as a diamine and 4.3g (14.3 mmol) of 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinicdianhydride were dissolved in 40 g of N-methylpyrrolidone, followed bystirring at 20° C. for 4 hours to carry out a polycondensation reaction,but polymerization did not substantially proceed, and only an oligomerwas formed. Further, heating was carried out, but no improvement ineffects was observed.

COMPARATIVE EXAMPLE 4

5 g (14.3 mmol) of hexadecyloxy-2,4-diaminobenzene as a diamine and 3.6g (14.3 mmol) of 3,5,6-tricarboxynorbornane-2:3,5:6 dianhydride weredissolved in 40 g of N-methylpyrrolidone, followed by stirring at 20° C.for 4 hours to carry out a polycondensation reaction, but polymerizationdid not substantially proceed, and only an oligomer was formed. Further,heating was carried out, but no improvement in effects was observed.

EXAMPLES 26 to 45

(Preparation of Liquid Crystal Alignment Films)

Then, a polyimide precursor or a polyimide solution obtained in one ofExamples 6 to 25 was coated on a glass substrate and heat-treated at180° C. to form a polyimide coating film, whereupon the tilt angle andthe uniformity in alignment of liquid crystal when used as a liquidcrystal alignment film, were measured in accordance with the followingmethods.

Evaluation of the tilt angle: a polyimide precursor or a polyimidesolution obtained in one of Examples 6 to 21 and Comparative Example 1was diluted with N-methylpyrrolidone or γ-butyrolactone to obtain asolution having a resin concentration of 5%, which was spin-coated on atransparent electrode-mounted glass substrate at a rotational speed of3500 rpm and heated at 80° C. for 10 minutes and at 250° C. for one hourto obtain a uniform polyimide coating film. After rubbing this coatingfilm with a cloth, such substrates were assembled so that the rubbingdirections were in parallel, with a spacer of 23 μm interposed, andliquid crystal (ZLI-2003, manufactured by Merck Company) was injected toprepare a cell having homeotropic or homogeneous alignment.

With respect to this cell, after heat treatment at 120° C. for one hour,the uniformity of liquid crystal alignment under a polarizationmicroscope was confirmed, and the tilt angle was measured by a crystalrotation method or a magnetic field quantitative method. The results areshown in Table 2.

TABLE 2 Example Polyimide Diamine Tilt angle Uniformity of No. (ExampleNo.) (Example No.) (°) alignment 26  6* 1 90 Uniform 27  7 1 90 Uniform28  8 1 90 Uniform 29  9 1 90 Uniform 30  11* 2 6 Uniform 31 11 2 2Uniform 32 12 2 3 Uniform 33 13 2 3 Uniform 34  14* 3 90 Uniform 35 15 390 Uniform 36 16 3 90 Uniform 37 17 3 90 Uniform 38  18* 4 90 Uniform 3919 4 90 Uniform 40 20 4 90 Uniform 41 21 4 90 Uniform 42  22* 5 90Uniform 43 23 5 90 Uniform 44 24 5 90 Uniform 45 25 5 90 Uniform Comp. 1 90 Non-uniform Ex. 1 *The polyimide precursor solution was employed.

INDUSTRIAL APPLICABILITY

The diaminobenzene derivative of the present invention can easily besynthesized and irrespective of the structure of the acid dianhydride,it has a high reactivity for swift polymerization, whereby thecorresponding polyimide having a high molecular weight can easily beobtained. Further, in the case of a polyimide for an alignment film fora liquid crystal display device, it is capable of aligning liquidcrystal uniformly, whereby a desired tilt angle can easily be obtained.

What is claimed is:
 1. A liquid crystal alignment film containing apolyimide obtained by reacting a diamine containing at least 1 mol % ofa diaminobenzene derivative represented by the general formula (1):

wherein each of X and P which are independent of each other, is asingle bond or a bivalent organic group selected from —O—, —COO—, —OCO—,—CONH— and —NHCO—, Q is a C₁₋₂₂ straight chain alkyl group or straightchain fluoroalkyl group with the proviso that when X is oxygen, P cannotbe a single bond, a is an integer of from 1 to 4 and represents thenumber of substituents, R is a substituent selected from fluorine, amethyl group and a trifluoromethyl group, and b is an integer of from 0to 4 and represents the number of substituents, with at least onecompound selected from a tetracarboxylic dianhydride and itsderivatives, to obtain a polyimide precursor having a reduced viscosityof from 0.05 to 5.0 dl/g in N-methylpyrrolidone at a temperature of 30°C., concentration: 0.5 g/dl and ring-closing it, and having a repeatingunit represented by the general formula (2):

wherein A is a tetravalent organic group constituting a tetracarboxylicacid, and B is a bivalent organic group constituting a diamine.
 2. Theliquid crystal alignment film according to claim 1, wherein thetetracarboxylic dianhydride is an alicyclic tetracarboxylic dianhydride.3. The liquid crystal alignment film according to claim 2, wherein thealicyclic tetracarboxylic dianhydride is at least one tetracarboxylicdianhydride selected from 1,2,3,4-cyclobutane tetracarboxylicdianhydride, bicyclo[3,3,0]-octane tetracarboxylic dianhydride,3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride and3,5,6-tricarboxynorbornane-2:3,5:6 dianhydride.
 4. The liquid crystalalignment film according to claim 1, wherein X is a single bond or abivalent organic group selected from —COO—, —OCO—, —CONH— and —NHCO—;and P is a single bond or a bivalent organic group selected from —O—,—COO—, —OCO—, —CONH— and —NHCO—.
 5. The liquid crystal alignment filmaccording to claim 1, wherein X is a single bond.
 6. The liquid crystalalignment film according to claim 1, wherein X is a bivalent organicgroup selected from —COO—, —OCO—, —CONH— and —NHCO—.
 7. The liquidcrystal alignment film according to claim 1, wherein X is a —COO— group.8. The liquid crystal alignment film according to claim 1, wherein X isa —OCO— group.
 9. The liquid crystal alignment film according to claim1, wherein X is a —CONH— group.
 10. The liquid crystal alignment filmaccording to claim 1, wherein X is a —NHCO— group.
 11. The liquidcrystal alignment film according to claim 1, wherein P is a single bond.12. The liquid crystal alignment film according to claim 1, wherein P isa —O— group.
 13. The liquid crystal alignment film according to claim 1,wherein P is a bivalent organic group selected from —COO—, —OCO—, —CONH—and —NHCO—.
 14. The liquid crystal alignment film according to claim 1,wherein P is a —COO— group.
 15. The liquid crystal alignment filmaccording to claim 1, wherein P is a —OCO— group.
 16. The liquid crystalalignment film according to claim 1, wherein P is a —CONH— group. 17.The liquid crystal alignment film according to claim 1, wherein P is a—NHCO— group.